qemu: Refactor config parameter retrieval
qemu: Refactor config parameter retrieval

This patch adds macros to help retrieve configuration values from qemu
driver's configuration. Some configuration options are grouped
together in the process.

iam-TJ/libvirt,rlaager/libvirt,elmarco/libvirt,fabianfreyer/libvirt,zhlcindy/libvirt-1.1.4-maintain,jardasgit/libvirt,nertpinx/libvirt,elmarco/libvirt,nertpinx/libvirt,libvirt/libvirt,agx/libvirt,fabianfreyer/libvirt,elmarco/libvirt,shugaoye/libvirt,bjzhang/libvirt,VenkatDatta/libvirt,jeckersb/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,taget/libvirt,agx/libvirt,cbosdo/libvirt,jeckersb/libvirt,agx/libvirt,trainstack/libvirt,andreabolognani/libvirt,rlaager/libvirt,shugaoye/libvirt,siboulet/libvirt-openvz,trainstack/libvirt,jfehlig/libvirt,eskultety/libvirt,andreabolognani/libvirt,nertpinx/libvirt,bjzhang/libvirt,bjzhang/libvirt,emaste/libvirt,datto/libvirt,zhlcindy/libvirt-1.1.4-maintain,jeckersb/libvirt,eskultety/libvirt,trainstack/libvirt,shugaoye/libvirt,agx/libvirt,emaste/libvirt,bjzhang/libvirt,taget/libvirt,jeckersb/libvirt,emaste/libvirt,olafhering/libvirt,zhlcindy/libvirt-1.1.4-maintain,libvirt/libvirt,jeckersb/libvirt,eskultety/libvirt,iam-TJ/libvirt,rlaager/libvirt,zippy2/libvirt,bjzhang/libvirt,eskultety/libvirt,fabianfreyer/libvirt,crobinso/libvirt,jeckersb/libvirt,jardasgit/libvirt,emaste/libvirt,rlaager/libvirt,emaste/libvirt,iam-TJ/libvirt,iam-TJ/libvirt,taget/libvirt,emaste/libvirt,taget/libvirt,iam-TJ/libvirt,zhlcindy/libvirt-1.1.4-maintain,jardasgit/libvirt,siboulet/libvirt-openvz,zippy2/libvirt,trainstack/libvirt,nertpinx/libvirt,jardasgit/libvirt,zhlcindy/libvirt-1.1.4-maintain,olafhering/libvirt,olafhering/libvirt,iam-TJ/libvirt,libvirt/libvirt,shugaoye/libvirt,siboulet/libvirt-openvz,iam-TJ/libvirt,trainstack/libvirt,fabianfreyer/libvirt,trainstack/libvirt,crobinso/libvirt,olafhering/libvirt,nertpinx/libvirt,siboulet/libvirt-openvz,VenkatDatta/libvirt,datto/libvirt,andreabolognani/libvirt,siboulet/libvirt-openvz,zippy2/libvirt,cbosdo/libvirt,taget/libvirt,emaste/libvirt,zippy2/libvirt,datto/libvirt,rlaager/libvirt,cbosdo/libvirt,andreabolognani/libvirt,cbosdo/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,trainstack/libvirt,eskultety/libvirt,elmarco/libvirt,libvirt/libvirt,jardasgit/libvirt,crobinso/libvirt,jfehlig/libvirt,datto/libvirt,datto/libvirt,VenkatDatta/libvirt,agx/libvirt,shugaoye/libvirt,VenkatDatta/libvirt,crobinso/libvirt,jeckersb/libvirt,elmarco/libvirt,cbosdo/libvirt,jfehlig/libvirt